Brian:
In Tedd Benson's book "Building the Timber Frame House, The Revival of a Forgotten Craft" with James Gruber, starting on page 103 there is a layout description showing which order to cut each line for a stop-splayed scarf joint with under-squinted butts and tabled with wedges.
There is also a rule about how long to make it, which I heard at the last eastern conference. That is the length of the scarf should be 2.5 or 3 times the height of the timbers. For example if your timbers are 8" tall then the scarf could be three times that or 24" long.
I'm sure there are other methods of laying out these joints, and some of the types of scarf joints are shown in Jack Sobon's History American Timber Joinery, A Graphic Guide, available from the guild.
I hope this is the type of joint you're looking for info on.
Jim Rogers

Whatever you do, have fun doing it!